The present invention generally relates to elongate probe assemblies of sufficiently miniaturized dimensions so as to be capable of navigating tortuous paths within a patient""s organs and/or vessels. In preferred forms, the present invention is embodied in automated units which are connectable to a probe assembly having a distally located ultrasound transducer subassembly which enables the transducer subassembly to be positioned accurately by an attending physician and then translated longitudinally (relative to the axis of the elongate probe assembly) within the patient under automated control.
I. Introductory Background Information
Probe assemblies having therapeutic and/or diagnostic capabilities are being increasingly utilized by the medical community as an aid to treatment and/or diagnosis of intravascular and other organ ailments. In this regard, U.S. Pat. No. 5,115,814 discloses an intravascular probe assembly with a distally located ultrasonic imaging probe element which is positionable relative to intravascular sites. Operation of the ultrasonic element in conjunction with associated electronic components generates visible images that aid an attending physician in his or her treatment of a patient""s vascular ailments. Thus, a physician may view in real (or essentially near real) time intravascular images generated by the ultrasonic imaging probe element to locate and identify intravascular abnormalities that may be present and thereby prescribe the appropriate treatment and/or therapy.
The need to position accurately a distally located operative probe element relative to an intravascular site using any therapeutic and/or diagnostic probe assembly is important so that the attending physician can confidently determine the location of any abnormalities within the patient""s intravascular system. Accurate intravascular position information for the probe assembly will also enable the physician to later replicate probe positions that may be needed for subsequent therapeutic and/or diagnostic procedures. For example, to enable the physician to administer a prescribed treatment regimen over time and/or to later monitor the effects of earlier therapeutic procedures.
Recently ultrasonic imaging using computer-assisted reconstruction algorithms has enabled physicians to view a representation of the patient""s interior intravascular structures in two or three dimensions (i.e., so-called three dimensional or longitudinal view reconstruction). In this connection, the current image reconstruction algorithms employ data-averaging techniques which assume that the intravascular structure between an adjacent pair of data samples will simply be an average of each such data sample. Thus, the algorithms use graphical xe2x80x9cfill inxe2x80x9d techniques to depict a selected section of a patient""s vascular system under investigation. Of course, if data samples are not sufficiently closely spaced, then lesions and/or other vessel abnormalities may in fact remain undetected (i.e., since they might lie between a pair of data samples and thereby be xe2x80x9cmaskedxe2x80x9d by the image reconstruction algorithms mentioned previously).
In practice, it is quite difficult for conventional ultrasonic imaging probes to obtain sufficiently closely spaced data samples of a section of a patient""s vascular system under investigation since the reconstruction algorithms currently available depend upon the software""s ability to process precisely longitudinally separated data samples. In this regard, conventional intravascular imaging systems depend upon manual longitudinal translation of the distally located ultrasound imaging probe element by an attending physician. Even with the most skilled physician, it is practically impossible manually to exercise constant rate longitudinal translation of the ultrasound imaging probe (which thereby provides for a precisely known separation distance between adjacent data samples). In addition, with manual translation, the physician must manipulate the translation device while observing the conventional two dimensional sectional images. This division of the physician""s attention and difficulty in providing a sufficiently slow constant translation rate can result in some diagnostic information being missed. In order to minimize the risk that diagnostic information is missed, then it is necessary to devote more time to conducting the actual imaging scan which may be stressful to the patient.
Thus, what has been needed in this art, is an ultrasound imaging probe assembly which is capable of being translated longitudinally within a section of a patient""s vascular system at a precise constant rate. Such an ability would enable a series of corresponding precisely separated data samples to be obtained thereby minimizing (if not eliminating) distorted and/or inaccurate reconstructions of the ultrasonically scanned vessel section (i.e., since a greater number of more closely spaced data samples could reliably be obtained). Also, such an assembly could be operated in a xe2x80x9chands-offxe2x80x9d manner which would then allow the physician to devote his attention entirely to the real time images with the assurance that all sections of the vessel were displayed. In terms of reconstruction, the ultrasound imaging probe could be removed immediately and the physician could interrogate the images or their alternative reconstructions on a near real time basis. Such a feature is especially important during coronary diagnostic imaging since minimal time would be needed to obtain reliable imaging while the blood flow through the vessels is blocked by the probe assembly. It is therefore towards fulfilling such needs that the present invention is directed.
II. Information Disclosure Statement
One prior proposal for effecting longitudinal movements of a distally located operative element associated with an elongate probe assembly is disclosed in U.S. Pat. No. 4,771,774 issued to John B. Simpson et al on Sep. 20, 1988 (hereinafter xe2x80x9cSimpson et al ""774xe2x80x9d). The device disclosed in Simpson et al ""774 includes a self-contained motor drive unit for rotating a distally located cutter element via a flexible drive cable with manual means to effect relative longitudinal movements of the rotating cutter element.
More specifically, in Simpson et al ""774, the proximal end of a flexible drive cable is slidably coupled to a hollow extension rotary drive shaft with a splined shaft. The hollow extension drive shaft is, in turn, coupled to a motor, whereas the splined shaft cooperates with a manually operated slide member. Sliding movements of the slide member relative to the motor drive unit housing translate into direct longitudinal movements of the flexible drive cable, and hence the distally located cutter element. In brief, this arrangement does not appear to allow for automated longitudinal movements of the distally located probe element.
The longitudinal position translator of the present invention is especially adapted for use with an intravascular probe assembly of type disclosed in the above-mentioned U.S. Pat. No. 5,115,814 (incorporated fully by reference hereinto). That is, the preferred intravascular probe assembly with which the position translator of the present invention may be used will include a flexible guide sheath introduced along a tortuous path of a patient""s vascular system, and a rotatable probe element (preferably an ultrasonic imaging probe) which is operatively introduced into the lumen of the guide sheath. Of course, the position translator of the present invention may be modified easily to accommodate less complex one-piece ultrasonic probe assemblies. Rotational movements supplied by a patient-external motor are transferred to a distally located transducer subassembly by means of a flexible torque cable which extends through the guide sheath.
As is described more completely in U.S. Pat. No. 5,115,814, the interior of the guide sheath provides a bearing surface against which the probe element rotates. This bearing surface supports the probe element during its rotation so that virtually no xe2x80x9cplayxe2x80x9d is presentxe2x80x94that is, so that the probe element rotates essentially coaxially relative to the vascular vessel undergoing therapy and/or investigation. The probe element is also longitudinally (i.e. axially) movable so that axial-spaced 360.degree. data sample xe2x80x9cslicesxe2x80x9d of the patient""s vascular vessel wall can be imaged.
The automated longitudinal position translator of the present invention generally includes a probe drive module and a linear translation module. The probe drive module is most preferably embodied in an elongate barrel-shaped housing structure having a manual positioning lever capable of reciprocal movements between advanced and retracted positions. The lever captures a proximal end of the guide sheath within which a probe element is disposed. A flexible torque cable connects the transducer subassembly at the distal end of the probe element to a drive shaft which is driven, in the preferred embodiment, by a precision rate-controlled motor located in a separate fixed base unit. Preferably, the housing is hinged in a xe2x80x9cclamshellxe2x80x9d fashion to more easily facilitate electrical and mechanical coupling of the intravascular probe assembly. The lever may be eliminated when using less complex one-piece ultrasonic probe assemblies or modified so as to capture the guide catheter or introducer.
The linear translation module supports the probe drive module. In addition, the linear translation module is coupled operatively to the probe drive module so as to allow for relative hinged movements thereby and thus permit the probe drive module to be moved between a manually-operable condition (whereby the probe drive module is disengaged from the longitudinal drive subassembly associated with the linear translation module to thereby allow a physician to exercise manual control over the longitudinal positioning of the probe element) and an automated condition (whereby the probe drive module is operatively engaged with the linear translation module so that automated longitudinal position control over the probe element can be exercised).
In use, the ultrasound imaging probe will be physically positioned by an attending physician within a section of a patient""s vascular system under investigation using conventional fluoroscopic positioning techniques. Thereafter, the proximal portion of the probe and guide sheath assembly will be coupled to the probe drive module. The probe drive module can then be employed to either manually or automatically translate the imaging probe element longitudinally within the section of the patient""s vascular system under investigation during an ultrasonic imaging scan of the same as may be desired by the attending physician by moving the probe drive module between its manual and automated conditions, respectively. The present invention thus allows the distally located probe element to be rotated, while simultaneously providing the attending physician with the capability of longitudinally translating the probe element at a constant automated translation rate to thereby obtain reliable data samples representative of longitudinally spaced-apart data xe2x80x9cslicesxe2x80x9d of the patient""s vascular section under investigation. These data xe2x80x9cslicesxe2x80x9d may then be reconstructed using conventional computer-assisted algorithms to present the entire section of the patient""s vascular system under investigation in a more informative xe2x80x9ctwo-dimensionalxe2x80x9d longitudinal or xe2x80x9cthree-dimensionalxe2x80x9d image display on a CRT (or other) monitor. The physician can thus manipulate the image orientation or two-dimensional sectional plane of the vascular section electronically and thereby achieve a more informative representation of the condition of the patient""s vascular section under investigation.
In its preferred embodiment, the linear position translator provides for automated translation of the imaging probe from a distal location to a proximal location only. Thus, the imaging probe would not be advanced under automated control into the guide sheath. Such a preferred functional attribute eliminates the need for sophisticated sensor and control systems to sense and stop probe advancement should it encounter a xe2x80x9ckinkxe2x80x9d or non-negotiable sharp bend in the guiding sheath. Furthermore, during probe withdrawal (i.e., distal to proximal motion), the guide sheath is supported by the probe and may not xe2x80x9ckinkxe2x80x9d. Also, since the probe has already negotiated all bends during its initial manual distal advancement, the attending physician is assured that the bends are in fact negotiable by the probe upon its withdrawal through that same path. Thus, although the preferred embodiment contemplates automated longitudinal translation in a proximal direction, it is likewise preferred that the attending physician advance the probe in a distal direction manually so that the physician may use his or her experience with the catheters and the tactile sensations to judge when an obstruction has been encountered.
Further features and advantages of the present invention will become more clear after careful consideration is given to the following detailed description of presently preferred exemplary embodiments.